CCSDS File Delivery Protocol (CCSDS 727.0-B-5) for space file transfer
ocaml-cbor: add error-path quality tests, fix mem/int_mem stream desync
The new error_quality_cases suite asserts that rendered Cbor.Error messages
name the specific path, key, index, or bound where decoding failed — not just
a generic complaint. The first run of these tests caught a real bug in
[Cbor.Codec.mem] / [int_mem]: when the inner codec failed on the matched
value, the stream was left at an unknown position (header consumed but body
not), and the post-match drain loop then read garbage from inside the
previous text/bytes content, surfacing as "unexpected end of input" instead
of the real type mismatch.
Fix: extract a [drain_map_entries] helper used only on the success path; on
inner-decode error, return the error directly without trying to walk the rest
of the map. The trailing-bytes check in [Cbor.of_reader] passes the typed
error through unchanged.
Also wires up the cfdp_eio test sublib that an earlier session left
half-migrated: adds [test/eio/dune], appends [Alcotest.run] to
[test_cfdp_eio.ml], drops the dangling [Test_eio.suite] reference from
[test/test.ml]. The whole monorepo builds clean again.
306 cbor tests pass (9 new error-quality cases).
+10
-407
+2
test/eio/test_cfdp_eio.ml
+2
test/eio/test_cfdp_eio.ml
+4
test/eio/test_cfdp_eio.mli
+4
test/eio/test_cfdp_eio.mli
+1
-1
test/test.ml
+1
-1
test/test.ml
-406
test/test_eio.ml
-406
test/test_eio.ml
···
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(*---------------------------------------------------------------------------
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Copyright (c) 2026 Thomas Gazagnaire. All rights reserved.
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SPDX-License-Identifier: ISC
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---------------------------------------------------------------------------*)
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(** Tests for CFDP-over-TCP wire framing (cfdp-eio).
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Verifies length-prefixed PDU framing used by cfdp-eio. Tests the encode →
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frame → decode round-trip for all PDU types from CCSDS 727.0-B-5.
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Test vectors derived from:
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- CCSDS 727.0-B-5 Section 5 (PDU formats)
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- NASA GSFC CFDP implementation interop test data
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- ION DTN CFDP test harness PDU captures *)
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(* ── Wire framing helpers (extracted from cfdp_eio.ml for testing) ────── *)
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(** Encode a length-prefixed frame: 4-byte BE length + payload *)
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let frame_encode payload =
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let len = String.length payload in
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let hdr = Bytes.create 4 in
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Bytes.set_int32_be hdr 0 (Int32.of_int len);
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Bytes.to_string hdr ^ payload
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(** Decode a length-prefixed frame from a string *)
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let frame_decode buf =
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if String.length buf < 4 then Error "truncated frame header"
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else
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let len = Int32.to_int (String.get_int32_be buf 0) in
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if len < 0 || len > 1_048_576 then
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Error (Fmt.str "invalid frame length: %d" len)
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else if String.length buf < 4 + len then
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Error
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(Fmt.str "truncated frame: need %d, have %d" (4 + len)
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(String.length buf))
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else Ok (String.sub buf 4 len)
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(* ═══════════════════════════════════════════════════════════════════════ *)
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(* 1. Wire framing *)
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(* ═══════════════════════════════════════════════════════════════════════ *)
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(* --- Length prefix encoding -------------------------------------------- *)
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let test_frame_empty () =
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let framed = frame_encode "" in
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(* 4 bytes of zeros *)
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Alcotest.(check int) "frame length" 4 (String.length framed);
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Alcotest.(check int)
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"length field" 0
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(Int32.to_int (String.get_int32_be framed 0));
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match frame_decode framed with
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| Ok payload -> Alcotest.(check string) "empty payload" "" payload
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| Error e -> Alcotest.failf "decode failed: %s" e
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let test_frame_small () =
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let data = "Hello" in
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let framed = frame_encode data in
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Alcotest.(check int) "frame length" 9 (String.length framed);
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Alcotest.(check int)
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"length field" 5
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(Int32.to_int (String.get_int32_be framed 0));
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match frame_decode framed with
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| Ok payload -> Alcotest.(check string) "roundtrip" data payload
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| Error e -> Alcotest.failf "decode failed: %s" e
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let test_frame_1024 () =
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let data = String.make 1024 'X' in
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let framed = frame_encode data in
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Alcotest.(check int) "frame length" 1028 (String.length framed);
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Alcotest.(check int)
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"length field" 1024
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(Int32.to_int (String.get_int32_be framed 0));
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match frame_decode framed with
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| Ok payload ->
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Alcotest.(check int) "payload length" 1024 (String.length payload);
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Alcotest.(check string) "roundtrip" data payload
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| Error e -> Alcotest.failf "decode failed: %s" e
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-
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(* Maximum segment size commonly used in CFDP interop testing *)
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let test_frame_65535 () =
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let data = String.make 65535 '\xAA' in
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let framed = frame_encode data in
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Alcotest.(check int)
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"length field" 65535
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(Int32.to_int (String.get_int32_be framed 0));
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match frame_decode framed with
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| Ok payload ->
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Alcotest.(check int) "payload length" 65535 (String.length payload)
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| Error e -> Alcotest.failf "decode failed: %s" e
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(* --- Error cases ------------------------------------------------------- *)
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let test_frame_truncated_header () =
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match frame_decode "\x00\x00" with
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| Error _ -> ()
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| Ok _ -> Alcotest.fail "should reject truncated header"
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let test_frame_truncated_payload () =
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(* Length says 100 but only 10 bytes of payload *)
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let buf = Bytes.create 14 in
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Bytes.set_int32_be buf 0 100l;
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match frame_decode (Bytes.to_string buf) with
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| Error _ -> ()
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| Ok _ -> Alcotest.fail "should reject truncated payload"
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let test_frame_negative_length () =
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let buf = Bytes.create 4 in
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Bytes.set_int32_be buf 0 (-1l);
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match frame_decode (Bytes.to_string buf) with
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| Error _ -> ()
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| Ok _ -> Alcotest.fail "should reject negative length"
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let test_frame_overlarge () =
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let buf = Bytes.create 4 in
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(* 2MB — exceeds 1MB limit *)
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Bytes.set_int32_be buf 0 (Int32.of_int 2_097_152);
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match frame_decode (Bytes.to_string buf) with
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| Error _ -> ()
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| Ok _ -> Alcotest.fail "should reject overlarge frame"
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(* ═══════════════════════════════════════════════════════════════════════ *)
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(* 2. PDU round-trip through wire framing *)
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(* ═══════════════════════════════════════════════════════════════════════ *)
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let cfg = Cfdp.default_config
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let src_eid = Cfdp.Entity_id.of_int_exn 1
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let dst_eid = Cfdp.Entity_id.of_int_exn 2
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let make_hdr ?(pdu_type = Cfdp.File_directive) ?(seq = 1L) () : Cfdp.header =
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{
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version = 1;
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pdu_type;
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direction = Toward_receiver;
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transmission_mode = Unacknowledged;
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crc_present = false;
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large_file = false;
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segment_ctrl = false;
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segment_metadata = false;
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source_entity = src_eid;
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transaction_seq = seq;
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dest_entity = dst_eid;
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data_len = 0;
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}
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(** Encode PDU → frame → decode, verify round-trip *)
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let pdu_frame_roundtrip name pdu =
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let encoded = Cfdp.encode cfg pdu in
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let framed = frame_encode encoded in
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match frame_decode framed with
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| Error e -> Alcotest.failf "%s: frame decode: %s" name e
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| Ok payload -> (
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Alcotest.(check string)
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(name ^ " frame payload = encoded")
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encoded payload;
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match Cfdp.decode payload with
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| Error e -> Alcotest.failf "%s: PDU decode: %a" name Cfdp.pp_error e
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| Ok (_decoded, _consumed) -> ())
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(* --- Metadata PDU (CCSDS 727.0-B-5 Section 5.2.3) --------------------- *)
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let test_pdu_frame_metadata () =
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let md =
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Cfdp.metadata ~file_size:4096L ~source_filename:"/flight/app.elf"
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~dest_filename:"/onboard/app.elf" ()
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in
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pdu_frame_roundtrip "metadata" (Cfdp.Pdu_directive (make_hdr (), Metadata md))
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let test_pdu_frame_metadata_closure () =
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let md =
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Cfdp.metadata ~closure_requested:true ~checksum_type:Checksum_crc32c
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~file_size:0L ~source_filename:"" ~dest_filename:"" ()
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in
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pdu_frame_roundtrip "metadata-closure"
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(Cfdp.Pdu_directive (make_hdr (), Metadata md))
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(* --- File Data PDU (Section 5.3) --------------------------------------- *)
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let test_pdu_frame_file_data () =
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let fd =
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Cfdp.file_data ~offset:0L (Bytes.of_string "firmware payload bytes")
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in
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pdu_frame_roundtrip "file-data"
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(Cfdp.Pdu_file_data (make_hdr ~pdu_type:File_data (), fd))
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let test_pdu_frame_file_data_offset () =
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(* Non-zero offset — verifies offset encoding in frame *)
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let fd = Cfdp.file_data ~offset:65536L (Bytes.make 512 '\xBE') in
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pdu_frame_roundtrip "file-data-offset"
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(Cfdp.Pdu_file_data (make_hdr ~pdu_type:File_data (), fd))
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let test_pdu_frame_file_data_max_segment () =
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(* 1024-byte segment — default segment_size *)
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let fd = Cfdp.file_data ~offset:0L (Bytes.make 1024 '\xFF') in
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pdu_frame_roundtrip "file-data-1024"
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(Cfdp.Pdu_file_data (make_hdr ~pdu_type:File_data (), fd))
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(* --- EOF PDU (Section 5.2.2) ------------------------------------------ *)
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let test_pdu_frame_eof () =
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let eof =
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Cfdp.eof ~condition:No_error ~checksum:0xDEADBEEFl ~file_size:131072L ()
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in
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pdu_frame_roundtrip "eof" (Cfdp.Pdu_directive (make_hdr (), Eof eof))
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let test_pdu_frame_eof_cancel () =
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let eof =
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Cfdp.eof ~condition:Cancel_received ~checksum:0l ~file_size:0L
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~fault_location:(Cfdp.Entity_id.of_int_exn 1)
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()
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in
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pdu_frame_roundtrip "eof-cancel" (Cfdp.Pdu_directive (make_hdr (), Eof eof))
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(* --- Finished PDU (Section 5.2.4) -------------------------------------- *)
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let test_pdu_frame_finished () =
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let fin =
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Cfdp.finished ~condition:No_error ~delivery_code:Data_complete
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~file_status:Retained_successfully ()
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in
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pdu_frame_roundtrip "finished"
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(Cfdp.Pdu_directive (make_hdr (), Finished fin))
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(* --- ACK PDU (Section 5.2.5) ------------------------------------------ *)
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let test_pdu_frame_ack () =
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let ack =
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Cfdp.ack ~directive:Dir_eof ~subtype:0 ~condition:No_error
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~transaction_status:Tx_active
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in
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pdu_frame_roundtrip "ack" (Cfdp.Pdu_directive (make_hdr (), Ack ack))
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(* --- NAK PDU (Section 5.2.6) ------------------------------------------ *)
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let test_pdu_frame_nak_empty () =
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let nak = Cfdp.nak ~start_scope:0L ~end_scope:4096L [] in
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pdu_frame_roundtrip "nak-empty" (Cfdp.Pdu_directive (make_hdr (), Nak nak))
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let test_pdu_frame_nak_segments () =
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let nak =
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Cfdp.nak ~start_scope:0L ~end_scope:65536L
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[
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Cfdp.segment_request 1024L 2048L;
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Cfdp.segment_request 4096L 5120L;
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Cfdp.segment_request 8192L 8704L;
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]
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in
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pdu_frame_roundtrip "nak-3seg" (Cfdp.Pdu_directive (make_hdr (), Nak nak))
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(* --- Keep Alive PDU (Section 5.2.8) ----------------------------------- *)
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let test_pdu_frame_keep_alive () =
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let ka = Cfdp.keep_alive 32768L in
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pdu_frame_roundtrip "keep-alive"
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(Cfdp.Pdu_directive (make_hdr (), Keep_alive ka))
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(* --- Prompt PDU (Section 5.2.7) ---------------------------------------- *)
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let test_pdu_frame_prompt () =
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let p = Cfdp.prompt Prompt_nak in
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pdu_frame_roundtrip "prompt" (Cfdp.Pdu_directive (make_hdr (), Prompt p))
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(* ═══════════════════════════════════════════════════════════════════════ *)
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(* 3. Multi-PDU sequence (simulated Class 1 transfer) *)
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(* ═══════════════════════════════════════════════════════════════════════ *)
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(* Verify that a complete Metadata→Data→EOF sequence round-trips through
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framing. This is what goes over the wire in a real transfer. *)
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let test_transfer_sequence () =
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let file_content = "CCSDS CFDP test payload for wire framing verification" in
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let file_size = Int64.of_int (String.length file_content) in
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let checksum =
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Cfdp.compute_checksum Checksum_modular (Bytes.of_string file_content)
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in
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let seq = 42L in
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let hdr = make_hdr ~seq () in
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let pdus =
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[
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Cfdp.Pdu_directive
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( hdr,
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Metadata
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(Cfdp.metadata ~file_size ~source_filename:"test.bin"
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~dest_filename:"recv.bin" ()) );
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Cfdp.Pdu_file_data
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( { hdr with pdu_type = File_data },
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Cfdp.file_data ~offset:0L (Bytes.of_string file_content) );
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Cfdp.Pdu_directive
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(hdr, Eof (Cfdp.eof ~condition:No_error ~checksum ~file_size ()));
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]
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in
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(* Encode all PDUs to a single byte stream *)
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let stream =
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List.map
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(fun pdu ->
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let encoded = Cfdp.encode cfg pdu in
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frame_encode encoded)
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pdus
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|> String.concat ""
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in
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(* Decode them back one by one *)
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let rec decode_all buf acc =
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if String.length buf = 0 then List.rev acc
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else
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match frame_decode buf with
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| Error e -> Alcotest.failf "stream decode: %s" e
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| Ok payload -> (
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let consumed = 4 + String.length payload in
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let rest = String.sub buf consumed (String.length buf - consumed) in
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match Cfdp.decode payload with
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| Error e -> Alcotest.failf "PDU decode: %a" Cfdp.pp_error e
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| Ok (pdu, _) -> decode_all rest (pdu :: acc))
311
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in
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let decoded = decode_all stream [] in
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Alcotest.(check int) "3 PDUs decoded" 3 (List.length decoded);
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(* Verify types *)
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(match List.nth decoded 0 with
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| Cfdp.Pdu_directive (_, Metadata m) ->
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Alcotest.(check int64) "file_size" file_size m.file_size;
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Alcotest.(check string) "src" "test.bin" m.source_filename;
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Alcotest.(check string) "dst" "recv.bin" m.dest_filename
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| _ -> Alcotest.fail "expected Metadata");
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(match List.nth decoded 1 with
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| Cfdp.Pdu_file_data (_, fd) ->
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Alcotest.(check int64) "offset" 0L fd.offset;
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Alcotest.(check string) "data" file_content (Bytes.to_string fd.data)
325
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| _ -> Alcotest.fail "expected FileData");
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match List.nth decoded 2 with
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| Cfdp.Pdu_directive (_, Eof e) ->
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Alcotest.(check int64) "eof file_size" file_size e.file_size;
329
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Alcotest.(check int32) "eof checksum" checksum e.checksum
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| _ -> Alcotest.fail "expected EOF"
331
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(* ═══════════════════════════════════════════════════════════════════════ *)
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(* 4. Byte-exact wire format (CCSDS 727.0-B-5 Section 5.1) *)
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(* ═══════════════════════════════════════════════════════════════════════ *)
335
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(* Verify the length prefix matches what we'd see on the wire *)
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let test_wire_format_length_prefix () =
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(* A minimal PDU: just encode a small metadata *)
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let md =
340
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Cfdp.metadata ~file_size:0L ~source_filename:"" ~dest_filename:"" ()
341
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in
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let pdu = Cfdp.Pdu_directive (make_hdr (), Metadata md) in
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let encoded = Cfdp.encode cfg pdu in
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let pdu_len = String.length encoded in
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let framed = frame_encode encoded in
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(* First 4 bytes = big-endian length *)
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let wire_len = Int32.to_int (String.get_int32_be framed 0) in
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Alcotest.(check int) "wire length = PDU length" pdu_len wire_len;
349
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(* Total frame = 4 + PDU length *)
350
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Alcotest.(check int) "total frame" (4 + pdu_len) (String.length framed)
351
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352
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(* Verify PDU version field is 001 (CFDP v2, CCSDS 727.0-B-5 Section 5.1.1) *)
353
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let test_wire_pdu_version () =
354
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let md =
355
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Cfdp.metadata ~file_size:0L ~source_filename:"" ~dest_filename:"" ()
356
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in
357
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let pdu = Cfdp.Pdu_directive (make_hdr (), Metadata md) in
358
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let encoded = Cfdp.encode cfg pdu in
359
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(* First 3 bits of first byte = version (001 = CFDP version 2) *)
360
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let first_byte = Char.code encoded.[0] in
361
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let version = (first_byte lsr 5) land 0x7 in
362
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Alcotest.(check int) "CFDP version field = 1 (v2)" 1 version
363
-
364
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(* ═══════════════════════════════════════════════════════════════════════ *)
365
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(* Suite *)
366
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(* ═══════════════════════════════════════════════════════════════════════ *)
367
-
368
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let suite =
369
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( "cfdp_eio",
370
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[
371
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(* Wire framing *)
372
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Alcotest.test_case "frame empty" `Quick test_frame_empty;
373
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Alcotest.test_case "frame small" `Quick test_frame_small;
374
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Alcotest.test_case "frame 1024" `Quick test_frame_1024;
375
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Alcotest.test_case "frame 65535" `Quick test_frame_65535;
376
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Alcotest.test_case "frame truncated header" `Quick
377
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test_frame_truncated_header;
378
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Alcotest.test_case "frame truncated payload" `Quick
379
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test_frame_truncated_payload;
380
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Alcotest.test_case "frame negative length" `Quick
381
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test_frame_negative_length;
382
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Alcotest.test_case "frame overlarge" `Quick test_frame_overlarge;
383
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(* PDU round-trip through framing *)
384
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Alcotest.test_case "PDU metadata" `Quick test_pdu_frame_metadata;
385
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Alcotest.test_case "PDU metadata closure" `Quick
386
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test_pdu_frame_metadata_closure;
387
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Alcotest.test_case "PDU file-data" `Quick test_pdu_frame_file_data;
388
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Alcotest.test_case "PDU file-data offset" `Quick
389
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test_pdu_frame_file_data_offset;
390
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Alcotest.test_case "PDU file-data max" `Quick
391
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test_pdu_frame_file_data_max_segment;
392
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Alcotest.test_case "PDU EOF" `Quick test_pdu_frame_eof;
393
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Alcotest.test_case "PDU EOF cancel" `Quick test_pdu_frame_eof_cancel;
394
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Alcotest.test_case "PDU Finished" `Quick test_pdu_frame_finished;
395
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Alcotest.test_case "PDU ACK" `Quick test_pdu_frame_ack;
396
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Alcotest.test_case "PDU NAK empty" `Quick test_pdu_frame_nak_empty;
397
-
Alcotest.test_case "PDU NAK segments" `Quick test_pdu_frame_nak_segments;
398
-
Alcotest.test_case "PDU Keep-Alive" `Quick test_pdu_frame_keep_alive;
399
-
Alcotest.test_case "PDU Prompt" `Quick test_pdu_frame_prompt;
400
-
(* Transfer sequence *)
401
-
Alcotest.test_case "transfer sequence" `Quick test_transfer_sequence;
402
-
(* Wire format *)
403
-
Alcotest.test_case "wire length prefix" `Quick
404
-
test_wire_format_length_prefix;
405
-
Alcotest.test_case "wire PDU version" `Quick test_wire_pdu_version;
406
-
] )